About a week ago I started using Pushbullet on my phone again. We all know that WhatsApp web sucks balls but I’m far to lazy to get the phone out of my pocket everytime someone sends me a WhatsApp message. Pushbullet then sends the messages to my always running Firefox where I can read and respond to them. The integrated end-to-end encryption feature in Pushbullet caught my attention so I set up an encryption password on my phone and in my browser but the Firefox AddOn wasn’t able to encrypt any of the forwarded messages. Instead it always showed me a prompt asking for the encryption password.
The cause of that issue was the Fanboy Social Blocking List in AdBlock Plus which blocked the Pushbullet AddOn page on which you set up the encryption password. After disabling ABP for the AddOn Page everything was working perfectly.